CHANGELOG.md: add 0.5.0

Prepare first release.

Author: bettio

CHANGELOG.md

@@ -5,3 +5,5 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+
+## [0.5.0] - 2022-03-22